1. Technical Field
The present invention relates to a droplet-ejection detecting device which detects ejections from nozzle orifices of a droplet ejecting head module and a recording apparatus incorporating the droplet-ejection detecting device.
Here, the word “recording apparatus” represents concepts including, for example, a printer (a serial printer, a line printer or the like), a facsimile and a copying machine. Also, the word “droplet ejecting head module” represents concepts including the “recording head module” of the “recording apparatus”. The word “recording head module” represents concepts including a recording head module mounted on a carriage which reciprocally moves in the width or line direction of recording and a fixed recording head module, so-called full-line type, mounted in the line printer which has a number of nozzle orifices arrayed over the entire length of the line of recording.
2. Related Art
Following description illustrates an ink jet printer as one example of a recording apparatus. The ink jet printer has a recording head module with a number of fine nozzle orifices provided therein. Ink droplets are ejected from the nozzle orifices when the ink jet printer performs recording, unavoidably involving a problem of clogging of each nozzle orifice. Especially, a line printer has a fixed recording head module with a numerous number of nozzle orifices arrayed over the entire length of the line of recording. Likewise, an industrial ink jet printer has tens of recording head modules with a numerous number of nozzle orifices arranged therein. When clogging leading to a failure of the ejection of the ink droplet happens, a white streak appears on the surface of a recording material carrying the recorded image, impairing the quality of recording.
Accordingly, a typical ink jet printer has a droplet-ejection detecting device provided therein which determines whether the ink droplets are safely ejected from the nozzle orifices of the recording head module. However, such a known droplet-ejection detecting device is configured to slowly move a recording head module with a plurality of nozzle orifices across a light path between a fixed laser-emitting source and a fixed light-receiving unit, so as to check each of the nozzle orifices one by one, as shown in JP-A-11-179884. Also, another droplet-ejection detecting device has electrodes arranged to receive electrostatically charged ink droplets to determine the state of ejection of the ink droplets by detecting the change in voltage of the electrode.
These known devices inconveniently take a few seconds per 1000 nozzle orifices to detect the ejections of the droplets from the nozzle orifices. Additionally, the device relying upon the voltage change is usable only on limited ink compositions.